Methods and apparatus for creating a high speed connection between a device under test and automatic test equipment

ABSTRACT

A clamping assembly is described for connecting a first plurality of contacts to a second plurality of contacts on a circuit board. The circuit board has a first outer face at an end and on one side of the circuit board, and a second outer face at the end and on the other side of the circuit board. The second contacts are arranged on at least one of the first and second outer faces. The circuit board also includes at least one first mechanical alignment feature. The clamping assembly includes a first assembly having a first inner face, and a second assembly having a second inner face substantially parallel to the first inner face. The first plurality of contacts are arranged on at least one of the first and second inner faces. At least one second mechanical alignment feature is operable in conjunction with the at least one first mechanical alignment feature on the circuit board to facilitate alignment of the first contacts with the second contacts. The first and second assemblies are configured to enable relative motion therebetween to effect clamping of the first and second inner faces to the first and second outer faces of the circuit board thereby electrically connecting the first and second contacts.

RELATED APPLICATION DATA

The present application is a continuation application of and claimspriority from U.S. patent application Ser. No. 10/965,245 (AttorneyDocket No. XANDP004C1), which is a continuation application of andclaims priority from U.S. patent application Ser. No. 10/725,966(Attorney Docket No. XANDP004), which claims priority from U.S.Provisional Patent Application No. 60/452,196 (Attorney Docket No.XANDP004P), the entire disclosure of each of which is incorporatedherein by reference for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates to techniques for reliably creating alarge number of high-speed electrical connections between two circuits.More specifically, the present invention provides a variety oftechniques for establishing such connections with a high cycle lifewhile requiring a very low externally-created force to facilitate theconnect-disconnect cycle.

With higher and higher parallelism required in high-speed electricalsystems (e.g., semiconductor test systems), the sum total of the forcenecessary to establish connections between circuits is becomingdifficult to overcome by mechanical means. In addition, the very natureof conventional interconnect schemes which are characterized by highcontact forces and metal-on-metal abrasion results in relatively lowcycle life due to the resulting damage to the noble metal plating on theelectrical contacts.

It is therefore desirable to provide techniques for establishinghigh-speed connections which do not suffer from the aforementioneddisadvantages.

SUMMARY OF THE INVENTION

According to various embodiments of the present invention, methods andapparatus are provided for connecting a first plurality of contacts to asecond plurality of contacts on a circuit board. The circuit board has afirst outer face at an end and on one side of the circuit board, and asecond outer face at the end and on the other side of the circuit board.The second contacts are arranged on at least one of the first and secondouter faces. The circuit board also includes at least one firstmechanical alignment feature. A clamping assembly designed according toa specific embodiment of the invention includes a first assembly havinga first inner face, and a second assembly having a second inner facesubstantially parallel to the first inner face. The first plurality ofcontacts are arranged on at least one of the first and second innerfaces. At least one second mechanical alignment feature is operable inconjunction with the at least one first mechanical alignment feature onthe circuit board to facilitate alignment of the first contacts with thesecond contacts. The first and second assemblies are configured toenable relative motion therebetween to effect clamping of the first andsecond inner faces to the first and second outer faces of the circuitboard thereby electrically connecting the first and second contacts.

According to some embodiments, the second contacts are arranged on oneof the first and second outer faces of the circuit board, and the firstcontacts are arranged on a corresponding one of the first and secondinner faces of the clamping assembly. According to alternativeembodiments, the second contacts are arranged on both of the first andsecond outer faces of the circuit board, and the first contacts arearranged on both of the first and second inner faces of the clampingassembly

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a device under test (DUT) printed circuit board assemblyand a corresponding tower assembly designed according to a specificembodiment of the invention.

FIG. 2 is a closer view of the DUT assembly of FIG. 1.

FIG. 3 is still a closer view of the DUT assembly of FIG. 1 showingdetailed features of the plurality of spine assemblies disposed thereon.

FIG. 4 is a closer view of the tower assembly of FIG. 1.

FIG. 5 is still a closer view of the tower assembly of FIG. 1illustrating the mechanism by which the tower assembly is secured to andaligned with the DUT assembly.

FIG. 6 is an even closer view of the tower assembly of FIG. 1 showingdetailed features of the plurality of clamping assemblies of which thetower assembly is comprised.

FIG. 7 is a view of the opposite side of the tower assembly.

FIG. 8 is a closer view of the side of the tower assembly shown in FIG.7 in which the interface between signal lines and the clampingassemblies is shown.

FIG. 9 is a view of the system in which the clamping assemblies and thecorresponding spine assemblies are aligned.

FIG. 10 is a cutaway view of the lifting and alignment mechanismscorresponding to the position of FIG. 9.

FIG. 11 is a view of the system in which the clamping assemblies and thecorresponding spine assemblies are in a pre-docking position.

FIG. 12 is a cutaway view of the lifting and alignment mechanismscorresponding to the position of FIG. 11.

FIG. 13 is a view of the system in which the clamping assemblies and thecorresponding spine assemblies are docked.

FIG. 14 is a cutaway view of the lifting and alignment mechanismscorresponding to the position of FIG. 13.

FIG. 15 is a view of the system in which the clamping assemblies areclamped onto the corresponding spine assemblies.

FIGS. 16A-16C show a perspective view of a clamping assembly and a spineassembly at various stages of the docking process.

FIGS. 17A-17C show a first end-on view of a clamping assembly and aspine assembly at various stages of the docking process.

FIGS. 18A-18C show a second end-on view of a clamping assembly and aspine assembly at various stages of the docking process.

FIGS. 19A-19C show a cross-section view of a clamping assembly and aspine assembly at various stages of the docking process.

FIG. 20 shows how the tower assembly of FIG. 1 may be connected to thetest electronics according to a specific embodiment of the invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Reference will now be made in detail to specific embodiments of theinvention including the best modes contemplated by the inventors forcarrying out the invention. Examples of these specific embodiments areillustrated in the accompanying drawings. While the invention isdescribed in conjunction with these specific embodiments, it will beunderstood that it is not intended to limit the invention to thedescribed embodiments. On the contrary, it is intended to coveralternatives, modifications, and equivalents as may be included withinthe spirit and scope of the invention as defined by the appended claims.In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Thepresent invention may be practiced without some or all of these specificdetails. In addition, well known features may not have been described indetail to avoid unnecessarily obscuring the invention.

According to a specific embodiment of the invention shown in FIG. 1, asystem 100 for establishing a large number of high-speed connectionsbetween automated test equipment (not shown) and at least one deviceunder test (DUT) (not shown). A DUT assembly 102 is provided on theunderside of which are a large number of electrical contacts (not shown)to one or more DUTs. Such electrical contacts might be, for example,probe needles if DUT assembly 102 is probe card for use in wafer sort,or sockets if DUT board 102 is a contactor board for use in packagetest. The primary function of DUT assembly 102 is to translateelectrical signals out of the plane of board 104 so that they areaccessible to the connection mechanism, i.e., interface tower assembly106.

Referring now to FIG. 2, DUT assembly 102 has a plurality of “spine”structures 202 disposed radially on board 104 which facilitate thesignal translation. A specific implementation of spines 202 is shown inFIG. 3. Each spine 202 comprises a rigid support assembly 302 whichincludes fine alignment slots 304 and 305. A flex circuit 306 fastenedto and supported by assembly 302 includes signal traces (not shown)which transmit signals between contacts 308 at the bottom of assembly302 to contacts 310 on either side of assembly 302. Contacts 308 matewith corresponding contacts (not shown) on the surface of board 104 whenspine 202 is secured in place.

According to a specific embodiment, support assembly 302 may includeflexible material 312 disposed as shown in assembly 302 which providecontact backup for contacts 308. According to some embodiments, similarcontact backup may be provided for contacts 310. While embodiments arecontemplated in which such contact backup is provided by the rigidmaterial of which assembly 302 is constructed, the flexible nature ofmaterial 312 ensures that the electrical connections made with contacts308 will have sufficient integrity despite any possible minor variationsin contact height. That is, to make the connection reliable across theentire connection array, there may either be a compressible member inthe system, or the flatness tolerance of the components may becontrolled to a very tight tolerance.

In the embodiment shown in FIG. 3, the compressible member is a piece ofsilicone rubber inserted into the spine behind the contacts. In anotherembodiment (see FIGS. 19A-19C)), the compressible member is a piece ofsilicone rubber that backs up each of the flexible circuits which clampdown onto the connections on the spine. In yet another alternativeembodiment, the clamping mechanism itself doubles as theflexible/compressible member. That is, silicone or urethane (i.e.,elastomeric) flexible bladders bear directly on the back of the flexiblecircuits and expand to create the required compressive force.

Referring once again to FIG. 2, DUT assembly 102 includes a centralassembly 204 which includes features by which the initial alignment ofassembly 102 to assembly 106 may be achieved. That is, assembly 204includes a central lifting point 206 by which DUT assembly 102 may bemoved up and down. In addition, kinematic couple alignment channelsdefined by cylindrical shafts 208 are provided which correspond tokinematic structures on tower assembly 106 (described below) and whichfacilitate securing of the relative positions of DUT assembly 102 andtower assembly 106 when the two assemblies are engaged with each other.More on the nature of this kinematic coupling will be described below.

It should be understood that the specific implementations of the DUTassembly and spines of FIGS. 1-3 are merely exemplary and that manyvariations of these basic structures are within the scope of theinvention. For example, board 104 is not restricted to the circulargeometry shown in the figures. Rather, any shape suitable for theparticular application, e.g., rectangular, may be employed. In addition,the configuration of the spines need not be as shown. That is, forexample, rather than the radial distribution depicted in FIGS. 1-3, thespines may be distributed in a rectilinear distribution. As a practicalmatter, any distribution of spines or equivalent structures asappropriate for a particular application may be employed.

Moreover, the structure of the spines themselves may vary considerablywithout departing from the scope of the invention. For example, insteadof employing the described flex circuit to route signals out of theplane of the DUT board, signal traces could be integral to the supportstructure itself which might comprise, for example, a printed circuitboard. Any physical structure which can translate signals out of theplane of the DUT board may be employed for this aspect of the invention.

Referring now to FIG. 4, interface tower assembly 106 includes aplurality of clamping connector assemblies 402 radially disposed ontower assembly frame 404. As mentioned above with reference to DUTassembly 102, the radial pattern shown is merely exemplary. As willbecome clear, connector assemblies 402 may be disposed in as manydifferent ways as spines 202 and, in fact, must correspond to thedistribution of spines on the associated DUT assembly.

Each connector assembly 402 corresponds to one of spines 202 on DUTassembly 102. When tower assembly 106 and DUT assembly 102 are engaged,each of spines 202 fits into a corresponding connector assembly 402, theinner walls of which have electrical contacts which correspond to andmake connections with contacts 310 on flex circuit 306.

According to a specific embodiment, engagement and coarse alignmentbetween DUT assembly 102 and tower assembly 106 is facilitated using apneumatic latch mechanism and a kinematic alignment system which aremore clearly illustrated in FIG. 5. A pneumatically powered latch 502receives lifting point 206 on DUT assembly 102 and pulls spring loadedkinematic alignment balls 504 into contact with kinematic alignmentshafts 208 on the DUT assembly. When springs (see FIGS. 10, 12, and 14))around the shaft connected to balls 504 are sufficiently compressed,balls 504 also come into contact with kinematic alignment shafts 508 onassembly 106. This kinematic arrangement resolves all six degrees offreedom, thereby inhibiting relative motion between DUT assembly 102 andtower assembly 106. It will be understood that the kinematic systemillustrated in these figures is only one of many possible mechanismswhich may be employed for this purpose.

FIG. 6 shows a closer view of a portion of an interface tower assembly106 in which contacts 602 on the inner walls of connector assemblies 402are apparent. The connection between contacts 602 and the correspondingcontacts 310 on spine assemblies 202 are facilitated by air cylinders604 which, once spines 202 are inserted into connector assemblies 402,force the opposing walls (i.e., connection boards 606) of each assembly402 against the opposing sides of the corresponding spine 202. Pressplates 608 are provided to ensure an even distribution of the forceexerted by air cylinders 604 across connection boards 606. The clampingforce is exerted via shafts 612 which extend from cylinder 604 throughthe near plate and are secured to the opposite side plate.Alternatively, clamping cylinders 604 may be replaced with othermechanisms such as, for example, expandable cylinders or bladders madeof silicone or urethane. These approaches are to be contrasted with theconventional approach in which a pogo stack contacts and is forciblycompressed against pads on the probe or contactor card in a directionnormal to the plane of the card.

According to various embodiments, contacts 308, 310, and 602 may beimplemented in a variety of ways. That is, the term “contacts” has beenused in the foregoing description to generically refer to a conductortermination which may form an electrical connection with anotherconductor termination, e.g., pads and bumps. It will be understood thatthe specific type of contact employed is immaterial as long assufficient connective integrity is maintained for the particularapplication.

FIG. 6 also shows springs 610 which work to keep connection boards 606apart against the action of clamping cylinders 604. Thus, in the eventof the loss of air pressure, clamping connector assemblies 402 willautomatically open. According to alternative embodiments, elasticspacers may be used to perform this function.

FIG. 7 shows tower assembly 106 from the opposite side of previousviews. Air cylinder 702 powers latch 502. Emergency brake 704 whichrequires air pressure to be released ensures that once assemblies 102and 106 are secured together they remain together even if there is aloss of power and/or air pressure. In fact, according to a specificembodiment, when the assemblies are docked, power is removed from aircylinder 702, and brake 704 is engaged, thereby making disengagement ofthe assemblies virtually impossible without reapplication of power.

A closer view of a portion of this side of tower assembly 106 is shownin FIG. 8. In this view, the upper portions of connection boards 606 canbe seen, attached to which are a plurality of shielded transmissionlines 802 for routing a variety of high-speed signals to and from testboards associated with the automated test equipment (not shown).Unshielded conductors 804 are also shown which provide connection andutility signals to and from connection boards 606. Air hoses 806 provideair pressure to clamping cylinders 604.

It should be noted that the functions served by connection boards 606and transmission lines 802 may be provided in a variety of ways withoutdeparting from the scope of the invention. According to a specificembodiment, connection boards 606 are implemented using flex circuits.According to an even more specific embodiment, both connection boards606 and transmission lines 802 are replaced with a flex circuit which isdesigned as described in commonly assigned, copending U.S. patentapplication Ser. No. 10/365,262 for FLEX-CIRCUIT-BASED HIGH SPEEDTRANSMISSION LINE filed on Feb. 11, 2003 (Attorney Docket No. XANDP003),the entire disclosure of which is incorporated herein by reference.

It should be noted at this point that the system described above may beused to provide repeatable connectivity for a wide variety ofapplications, some of which relate to the high-speed testing ofsemiconductor wafers or electronic circuits. It should also beunderstood that the parallelism represented by the system describedabove may be leveraged in a variety of ways to take full advantage ofthe invention. For example, most or all of the connectivity provided bysuch a system could be used to simultaneously test an entire wafer(e.g., 8 inches or larger). Alternatively, a large number of separateand distinct DUTs might be connected to each spine on the DUT assembly,allowing for the simultaneous testing and verification of hundreds ofdevices.

The kinematic coupling described above ensures a precise and repeatablealignment between the DUT assembly and the tower assembly. According tovarious embodiments of the invention, a degree of “independentsuspension” is provided for each of the clamping connector assemblieswith respect to the tower assembly of which they are a part. This allowsfor some self-alignment of the clamping connector assemblies to thespines on the DUT assembly which, as will be discussed, both simplifiesthe overall design as well as ensures the reliable and repeatablealignment of the contacts on both assemblies. The manner in which thisindependent suspension is accomplished according to a specificembodiment of the invention will be described below with reference toFIGS. 16-19.

According to a specific embodiment and as will be described withreference to FIGS. 9-15, this independent suspension allows eachclamping connector assembly to “float” in all axes. FIGS. 9-15illustrate the alignment, docking, and clamping functionalities of theembodiment of the invention described herein.

Initial alignment between the tower assembly and the DUT assembly (shownin FIG. 9) is achieved by inserting the DUT assembly's lifting point 206into lifting point receiver 502, and bringing kinematic alignment balls504 on the tower assembly into contact with the kinematic alignmentchannels on the DUT assembly as shown in FIG. 10. As shown in FIG. 9,this brings spine assemblies 202 into a coarse alignment with clampingconnector assemblies 402.

In the pre-docking position of FIG. 11, spines 202 are brought intocloser proximity with their corresponding connector assemblies 402. Asshown in FIG. 12, this is achieved when the DUT assembly has been liftedsufficiently such that the top of lifting point 206 is above latchingballs 1202. At this point, lifting point air cylinder 702 is energized,causing latching balls 1202 to be driven inward and under the top oflifting point 206. Spring 1205 around shaft 1206 associated with eachkinematic alignment ball 504 is compressed as shown, pushing theopposing end of shaft 1206 upward.

As mentioned above, the kinematic system of this embodiment allows for aprecise and repeatable alignment between the two major assemblies.However, given the level of parallelism and the number of subassemblieson each assembly which must be precisely aligned, an alignment system isprovided which independently aligns each clamping connector assemblywith its corresponding spine assembly. That is, each clamping connectorassembly 402 has two shafts (shafts 612 of FIG. 6) which mate with thecorresponding alignment slots 304 and 305 on spine 202 to achieve thedocked position of FIG. 13. Because of the fact that clamping connectorassemblies 402 are able to move independently in all axes, when thesepairs of shafts are engaged, independent and precise alignment isachieved between the contacts on each spine 202 and the correspondingcontacts on the connection boards or flex circuits of the associatedclamping connector assembly 402.

In any case, this freedom of movement in combination with the localalignment mechanisms for each clamping connector/spine pair and theclamping action provided by the clamping devices compensates for minorvariations in spine orientation with respect to any of x, y, z, pitch,roll, or yaw, thereby decreasing dependence on the kinematic system foraligning the contacts on every spine with the corresponding contacts onevery clamping connector.

The docked position of FIG. 13 is achieved by the action of liftingpoint air cylinder 702 on lifting point 206 and the resulting action ofthe kinematic system. As shown in FIG. 14, air cylinder 702 lifts theDUT assembly until each kinematic alignment ball 504 stops furtherlifting by coming to rest against the bottom and top kinematic alignmentchannels (i.e., the channels defined by shafts 208 of FIG. 2 and shafts508 of FIG. 5). Because air cylinder 702 has not bottomed, lifting point206 (and therefore the DUT assembly) is being held in place at thispoint by the lifting action of the air cylinder which, because of thecontinuous pressure which maintains the kinematic alignment balls in thekinematic alignment grooves, maintains alignment between the DUTassembly and the tower assembly.

Once the assemblies are in the docked position of FIG. 13, the airsignal to emergency brake 704 is removed and the brake is engaged. Thus,even if air pressure to the system is lost the DUT assembly would remainin position, a desirable result from both a safety perspective and acost perspective.

Once the DUT assembly and the tower assembly are in the docked positionof FIGS. 13 and 14, air signals to clamping cylinders 604 are assertedwhich exert force via shafts 612 thereby causing each clamping connectorassembly to clamp onto the inserted spine assembly, establishing theelectrical connections between the contacts (e.g., pads or bumps) on thespine's flex circuit and the corresponding contacts on the connectionboards (e.g., bumps or pads). An illustration of this clamped positionis shown in FIG. 15.

A more detailed description of a particular mechanism for achieving theindependent suspension of the individual clamping assemblies will now beprovided with reference to FIGS. 16-19. FIGS. 16A-16C show isolatedviews of a clamping assembly 402 and a spine assembly 202 in relativepositions corresponding to FIGS. 11, 13, and 15, respectively. Eachplate 608 of clamping assembly 402 includes an elastomer grommet 1602having flexible spokes centered on a plastic bushing 1604 through whicha shaft 1606 extends. Grommets 1602 and bushings 1604 are able to slidealong shaft 1606 which is secured in a corresponding groove at the outeredge of assembly 404.

Assembly 402 is secured to the inner edge of assembly 404 via urethanestructure 1608. The flexible natures of grommets 1602 and structure 1608provide the independent suspension which, together with the localmechanical alignment features described above, enables the precisealignment of each individual pair of assemblies 202 and 402.

FIGS. 17A-17C and FIGS. 18A-18C show end-on views of the same isolatedpair of assemblies in the various stages of docking. The views of FIG.17 are from the outer edge of assembly 404 looking toward its center,and those of FIG. 18 are from the center looking out. Local alignmentfeatures 304 and 305 of assembly 202 engage the lower shafts 612 coupledto cylinder 604 (the one in FIG. 17A being obscured by shaft 1606), andeffect the alignment of the electrical connections on the respectiveassemblies. As can be seen in FIGS. 17B and 18B, the independentsuspension of assembly 402 (most clearly illustrated in FIG. 17B by thedeformation of flexible structure 1608) results in the assembly beingraised up slightly with respect to its previous position in FIGS. 17Aand 18A. As can be seen in FIG. 18C, structure 1608 is further deformedas clamping cylinder 604 causes assembly 402 to clamp onto assembly 202.

FIGS. 19A-19C provide cross-sectional views of the views of FIGS.17A-17C. In this embodiment, clamping cylinder 604 employs an inflatablebladder 1902 which, when inflated, pulls left plate 608A and pushesright plate 608B together via the action of shafts 612 extending throughthe right plate and attaching to the left. Also shown in these figuresis the use of flexible material 1904 in plates 608 behind connectionboards 606 to provide backing for the contacts on connection boards 606.As discussed above with reference to FIG. 3, this ensures that theelectrical connections made with the contacts on assembly 202 will havesufficient integrity despite any possible minor variations in contactheight.

According to a specific embodiment, another set of clamping assembliesis employed to connect clamping assemblies 402 with the test electronicsin the test equipment. An example of how this may be accomplished isshown in FIG. 20. Many of the clamping assemblies and various othersystem components have been removed from the drawing for clarity. Torelate the illustrated context to previous figures, clamping assembly402 is shown clamped to one of spine assemblies 202 on DUT assembly 102.

Clamping assembly 402 is also connected back-to-back (via conductors 802and 804) with another clamping assembly (not shown) which clamps ontoone of test connection boards 2002. This is accomplished in a mannersimilar to that described above with respect to the docking processbetween assemblies 202 and 402. One such clamping assembly 2004 is shownhaving conductors 802 and 804 to which a clamping assembly 402 (notshown) is connected back-to-back. Test connection boards 2002 are eitherpart of, or are connected to, one or more PE boards which carry signalsto and from the test equipment. In this way, connections to the systemtest electronics are provided to the devices under test connected to DUTassembly 102.

While the invention has been particularly shown and described withreference to specific embodiments thereof, it will be understood bythose skilled in the art that changes in the form and details of thedisclosed embodiments may be made without departing from the spirit orscope of the invention. For example, some of the descriptions ofembodiments herein imply a certain orientation of various assemblies ofwhich the system is constructed. It will be understood, however, thatthe principals of the present invention may be employed in systems havea variety of spatial orientations and that therefore the inventionshould not be limited to the specific orientations shown.

According to a particular alternative, instead of a plurality of spineassemblies on a horizontally disposed board, the DUT assembly maycomprise a plurality of vertically disposed DUT boards (e.g., printedcircuit boards). According to this approach, the end of each board takesthe place of one of the spines in the above-described embodiments. Eachclamping assembly in the tower clamps on the end of a corresponding oneof the vertical boards.

In addition, although various advantages, aspects, and objects of thepresent invention have been discussed herein with reference to variousembodiments, it will be understood that the scope of the inventionshould not be limited by reference to such advantages, aspects, andobjects. Rather, the scope of the invention should be determined withreference to the appended claims.

1. A clamping assembly for connecting a first plurality of contacts to asecond plurality of contacts on a circuit board, the circuit boardhaving a first outer face at an end and on one side of the circuitboard, and a second outer face at the end and on the other side of thecircuit board, the second contacts being arranged on at least one of thefirst and second outer faces, the circuit board also including at leastone first mechanical alignment feature, the clamping assemblycomprising: a first assembly having a first inner face; a secondassembly having a second inner face substantially parallel to the firstinner face; the first plurality of contacts arranged on at least one ofthe first and second inner faces; and at least one second mechanicalalignment feature operable in conjunction with the at least one firstmechanical alignment feature on the circuit board to facilitatealignment of the first contacts with the second contacts; wherein thefirst and second assemblies are configured to enable relative motiontherebetween to effect clamping of the first and second inner faces tothe first and second outer faces of the circuit board therebyelectrically connecting the first and second contacts.
 2. The clampingassembly of claim 1 wherein the first and second inner faces of theclamping assembly comprise rigid circuit boards each having a pluralityof conductors embedded therein electrically connected to the firstcontacts.
 3. The clamping assembly of claim 2 wherein the rigid circuitboards are removable.
 4. The clamping assembly of claim 1 wherein thefirst and second inner faces of the clamping assembly comprise flexiblecircuits each having a plurality of conductors embedded thereinelectrically connected to the first contacts.
 5. The clamping assemblyof claim 4 wherein the flexible circuits are removable.
 6. The clampingassembly of claim 1 wherein the actuator is operable to force the firstand second inner faces of the clamping assembly toward each other,thereby clamping the first and second inner faces to the first andsecond outer faces of the circuit board.
 7. The clamping assembly ofclaim 1 wherein interaction between the first and second mechanicalalignment features constrains movement of the clamping assembly relativeto three degrees of freedom.
 8. The clamping assembly of claim 7 whereinclamping of the first and second inner faces of the clamping assembly tothe first and second outer faces of the circuit board further constrainsmovement of the clamping assembly relative to an additional threedegrees of freedom.
 9. The clamping assembly of claim 8 wherein the sixdegrees of freedom comprise x, y, z, pitch, roll, and yaw.
 10. Theclamping assembly of claim 1 wherein the at least one second mechanicalalignment feature on the clamping assembly comprises a first shaft and asecond shaft, and wherein the at least one first mechanical alignmentfeature on the circuit board comprises a groove near a first corner ofthe end of the circuit board configured to receive the first shaft, anda surface near a second corner of the end of the circuit boardconfigured to contact the outer surface of the second shaft.
 11. Theclamping assembly of claim 10 wherein interaction of the first shaft andthe groove constrain movement of the clamping assembly in two lineardimensions, and wherein interaction of the second shaft and the surfaceconstrain movement of the clamping assembly in one angular dimension.12. The clamping assembly of claim 1 wherein the second contacts arearranged on one of the first and second outer faces of the circuitboard, and wherein the first contacts are arranged on a correspondingone of the first and second inner faces of the clamping assembly. 13.The clamping assembly of claim 1 wherein the second contacts arearranged on both of the first and second outer faces of the circuitboard, and wherein the first contacts are arranged on both of the firstand second inner faces of the clamping assembly.
 14. The clampingassembly of claim 1 further comprising an actuator operable to effectthe relative motion between the first and second assemblies.
 15. Theclamping assembly of claim 14 wherein the actuator comprises anexpandable bladder.
 16. An electronic testing system comprising: atleast one circuit board, each circuit board having a first outer face atan end and on one side of the circuit board, a second outer face at theend and on the other side of the circuit board, first contacts arrangedon at least one of the first and second outer faces, and at least onefirst mechanical alignment feature; and at least one clamping assemblycorresponding to each circuit board, each clamping assembly including afirst assembly having a first inner face, a second assembly having asecond inner face substantially parallel to the first inner face, asecond plurality of contacts arranged on at least one of the first andsecond inner faces, and at least one second mechanical alignment featureoperable in conjunction with the at least one first mechanical alignmentfeature on the corresponding circuit board to facilitate alignment ofthe second contacts with the first contacts; wherein the first andsecond assemblies of each clamping assembly are configured to enablerelative motion therebetween to effect clamping of the first and secondinner faces to the first and second outer faces of the correspondingcircuit board thereby electrically connecting the first and secondcontacts.